This study entailed the development of two different carbon dioxide laser systems (one was a prototype pulsed system with fiber optics delivery and the other was a modification of a commercial medical carbon dioxide laser). Additionally a prototype (mode-locked or Q-switched) pulsed Nd:YAG laser coupled to a slit lamp was used. These laser systems were tested in a series of animal experiments (in rabbits and monkeys) to test the efficacy and safety of cutting vitreal membranes. The carbon dioxide laser systems were designed to be an adjunct to standard mechanical vitreous surgery, whereas the Nd:YAG laser-slit lamp system was for more minor operations entailing the transection of selected membranes without incision to remove debris. For both types of laser systems systematic studies of animal vitrecomies were performed in order to characterize laser pulse characteristics necessary to transect vitreal membranes. Additional studies of retinal damage as a function of pulse characteristics and distance of cutting site from the retina clarified the potential for use of these laser systems close to the retina. Preliminary data reveals that the carbon dioxide laser can cut experimentally created membranes in rabbits for virtually any condition of the clarity of the optical media. The Nd:YAG laser pulses can cut vitreal membranes when power densities exceeding 1 GW/square centimeter are achieved at the target. Moderate to severe turbidity of the optical media greatly decreases the ability to cut vitreal membranes with the Nd:YAG laser and create the potential for increased retinal damage. The Nd:YAG laser can not be used within 2 mm. of the retina without significant risk of retinal damage due to the absorption of radiation by the outer retina. The CO2 laser systems can be used within 2 mm. of the retina safely only when short duration pulses are used at a slow repetition rate in order to prevent the establishment of convective currents of hot vitreous. The CO2 laser is appropriate for cutting vascular membranes due to thermal coagulation of blood vessels accompanying the cutting action, whereas the use of the Nd:YAG laser in these cases without previous coagulation of vessels would result in vitreal hemorrhage.